Claremont Colleges Research Team Discovers World’s Fastest Land Animal

Paratarsotomus macropalpis, the fastest land animal as measure by body lengths per second

Relative to its size,
a Southern California mite runs faster than any other animal and thrives in
temperatures that would kill most other animals – according to new research by
a team led by Prof. Jonathan Wright.

Although the mite Paratarsotomus macropalpis is no bigger
than a sesame seed, it was recently recorded running at up to 322 body lengths
per second, a measure of speed that reflects how quickly an animal moves
relative to its body size. The previous record-holder, the Australian tiger
beetle, tops out at 171 body lengths per second. By comparison, a cheetah
running at 60 miles per hour attains only about 16 body lengths per second.

Extrapolated to the
size of a human, the mite’s speed is equivalent to a person running roughly
1300 miles per hour.

The mite is local to
Southern California and is often found running along rocks or sidewalks. First
identified in 1916, little is known about the mite’s habits or food sources.

Rubin presented
their findings at the findings
during the Experimental Biology 2014 meeting on April 27 and at the American Physiological Society Undergraduate
Research Poster Session on April 28. Since then, news of the discovery has rocketed around science media, with stories appearing in Science Daily, Science, Discovery and Nature World News, among others.

“It’s so cool to discover something
that’s faster than anything else, and just to imagine, as a human, going that
fast compared to your body length is really amazing,” said Rubin.

Wright became
interested in the mites while studying the effect of muscle biochemistry on how
quickly animals can move their legs. But it wasn’t until Young and Rubin
documented the mites’ running speeds in their natural environment that the team
knew they had found a new world record.

“Both relative speed
and stride frequency increase as animals get smaller,” explains Wright, “and in
theory, muscle physiology should at some point limit how fast a leg can move.
We were looking at the overarching question of whether there is an upper limit
to the relative speed or stride frequency that can be achieved. When the values
for mites are compared with data from other animals, they indicate that, if
there is an upper limit, we haven't found it yet.”

The research team used
high-speed cameras to record the mites’ sprints in the laboratory and in their
natural environment. “It was actually quite difficult to catch them, and when
we were filming outside, you had to follow them incredibly quickly as the
camera’s field of view is only about 10 centimeters across,” said Rubin.

The research team was
also surprised to find the mites running on concrete up to 140 degrees
Fahrenheit (60 degrees Celsius), a temperature significantly higher than the
upper lethal temperature of most animals. “They’re operating at temperatures
that seem to preclude activities of any other animal group. We’ve seen them
running where there were no other animals visibly active,” said Wright.

The mites also are
adept at stopping and changing directions extremely quickly, attributes the
researchers are investigating further for potential insights that may be
relevant to bioengineering applications.

The
research was funded by the Howard Hughes Medical Institute Undergraduate
Science Program. The Claremont Colleges’ HHMI grant funds approximately 50
summer undergraduate research projects each year.

“This
project is a really great example of collaborative research across the
Claremont Colleges,” says Wright. “We had students from two different campuses
and faculty from two campuses and two different fields.”